Sulfolane is a compound which is used principally as a solvent for extraction of benzene, toluene and xylene from mixtures with aliphatic hydrocarbons. Sulfolanes are also useful for a variety of other purposes, such as pesticidal compositions, textile applications, polymer solvent, acid gas treating, intermediates in the production of other organic chemicals, and solvents for various hydrocarbons, fatty acids, or fatty acid esters.
Because of its high dielectric constant, low volatility, and solubilizing characteristics, sulfolane is also useful for a wide variety of electronic and electrical applications, e.g. as a coil insulating component, battery solute, capacitor impregnate, and solvent in electroplating baths.
The production of sulfolane is well known by those familiar in the art and is disclosed in numerous references, such as U.S. Pat. No. 3,514,469, issued to J. E. Phillips et al., which patent is incorporated herein by reference. Crude sulfolanes are generally prepared by reacting sulfur dioxide with a sulfolene precursor to form a sulfolene. The resulting sulfolene is then catalytically hydrogenated to form the sulfolane. In its pure state, sulfolane is a colorless, highly polar, water soluble compound. Crude, or so called technical grade, sulfolane compound widely produced for use in extractive distillations, however, generally contains small amounts of impurities, such as insoluble sulfones, polymeric substances and other conversion products, which impart light brown color and turbidity to the crude sulfolane.
Recent interest in preparing low-color, low-turbidity sulfolane comes from new uses of sulfolane in electrical or electronic applications, such as preparing compositions for cleaning electronic circuit boards. In preparing compositions for cleaning electronic circuit boards, color and turbidity characteristics of the sulfolane used in the preparation of the circuit board cleaning compound are extremely important.
Accordingly, it is an object to this invention to provide a convenient process for the purification of crude sulfolane.
It is another object of this invention to provide a process which is safe, effective, simple and economical.
It is another object of this invention to recover liquid sulfolane having low-color and low-turbidity characteristics.